1. Technical Field
The present disclosure relates to a wireless network system for interconnecting a wireless network and another network different from the wireless network, and more particularly to a wireless network system for selecting an optimum one of a plurality of gateways, thereby enabling an interconnection between networks.
2. Related Art
The related-art documents related to a wireless network system for interconnecting a conventional wireless network and another network different from the conventional wireless network are as follows:    Japanese Patent Unexamined Documents: JP-A-2000-196674, JP-A-2003-258704, JP-T-2004-514339, JP-A-2005-167609 and JP-A-2005-268988.
FIG. 6 is a block diagram showing an example of a conventional wireless network system. In FIG. 6, wireless nodes 1, 2, 3, 4, 5 and 6 establish a mesh type of a wireless network and carry out a communication through the wireless network, A gateway 7 interconnects the wireless network to an Internet Protocol (IP) network, A control device 8 such as a computer carries out a communication through the IP network, and an IP network 100 is shown.
The wireless node 1 is interconnected to adjacent wireless nodes 3, 4 and 2 using wireless lines “WN01”, “WN02” and “WN03” as shown in FIG. 6. Similarly, wireless nodes 2, 3, 4, 5 and 6 are also interconnected to the adjacent wireless nodes properly using wireless lines “WN04”, “WN05”, “WN07”, “WN08” and “WN09” as shown in FIG. 6.
Furthermore, the wireless nodes 2, 4 and 6 are interconnected to the gateway 7 using wireless lines “WN10”, “WN11” and “WN12” as shown in FIG. 6, respectively. Then, a wireless network shown in a broken line of FIG. 6 is established.
In addition, the gateway 7 is interconnected to the IP network 100, and also the control device 8 is interconnected to the IP network 100.
Moreover, FIG. 7 is a block diagram showing a specific example of the wireless node. In FIG. 7, wireless communication means 9 carries out a communication through a wireless network (a wireless line), calculation control means 10 controls a whole wireless node such as a Central Processing Unit (CPU), storing means 11 stores data and information for a communication path search, and storing means 12 stores a program to control the wireless node. Furthermore, the wireless communication means 9, the calculation control means 10, the storing means 11 and storing means 12 constitute a wireless node 50.
The wireless communication means 9 is interconnected to a wireless network (a wireless line), and an input/output of the wireless communication means 9 is interconnected to the calculation control means 10. Moreover, the storing means 11 and the storing means 12 are also interconnected to the calculation control means 10.
The calculation control means 10 reads and executes a stored program from the storing means 12 to control the whole wireless node, and the wireless communication means 9 is controlled based on information stored in the storing means 11 to establish a wireless network together with the adjacent wireless node, thereby transferring data from each other. Thus, the calculation control means 10 is operated as the wireless node.
FIG. 8 is a block diagram showing a specific example of the gateway. In FIG. 8, wireless communication means 13 carries out a communication through a wireless network (a wireless line), calculation control means 14 controls a whole gateway such as a CPU, communication means 15 carries out a communication through an IP network (not shown), storing means 16 stores a program to control the gateway, and storing means 17 stores information for a protocol conversion. Moreover, the wireless communication means 13, the calculation control means 14, the communication means 15, the storing means 16 and the storing means 17 constitute a gateway 51.
The wireless communication means 13 is interconnected to a wireless network (a wireless line), and an input/output of the wireless communication means 13 is interconnected to the calculation control means 14. Moreover, the communication means 15 is interconnected to the IP network and has an input/output interconnected to the calculation control means 14. Furthermore, the storing means 16 and the storing means 17 are interconnected to the calculation control means 14.
The calculation control means 14 reads and executes the program stored in the storing means 16 to control the whole gateway, and controls the wireless communication means 13 based on the information stored in the storing means 17 to establish a wireless network together with the adjacent wireless node, thereby transferring data from each other. On the other hand, the calculation control means 14 controls the communication means 15 to carry out a data transfer together with the IP network 100.
Furthermore, the calculation control means 14 converts a protocol of data received through the wireless communication means 13 or the communication means 15 based on the information for a protocol conversion which is stored in the storing means 17 and transfers the data subjected to the protocol conversion through the communication means 15 or the wireless communication means 13. Thus, the calculation control means 14 is operated as the gateway.
An operation according to the conventional example shown in FIG. 6 will be described with reference to FIGS. 9, 10, 11 and 12. FIG. 9 is a flowchart for explaining an operation of each wireless node, FIGS. 10 and 12 are diagrams for explaining a data transfer, and FIG. 11 is a flowchart for explaining an operation of the gateway 7.
At “S001” in FIG. 9, the wireless node (more specifically, the calculation control means 10) determines whether to transfer data to the control device 8 (the IP node) through the IP network 100.
At “S001” in FIG. 9, if the wireless node determines to transfer the data, the wireless node (more specifically, the calculation control means 10) searches a transfer path to the gateway 7 and establishes a transfer path at “S002” in FIG. 9 and the wireless node (more specifically, the calculation control means 10) transfers the data to the gateway 7 using the established transfer path at “S003” in FIG. 9.
For example, if the wireless node 1 (more specifically, the calculation control means in the wireless node 1) determines to transfer the data, the wireless node 1 searches and establishes a transfer path using wireless lines “WN02” and “WN11” in FIG. 10 and the wireless node 1 (more specifically, the calculation control means in the wireless node 1) transfers the data to the gateway 7 as shown in “SD21” of FIG. 10.
Meanwhile, at “S101” in FIG. 11, the gateway 7 (more specifically, the calculation control means 14) determines whether the data is received through a wireless network or not.
At “S101” in FIG. 11, if the gateway 7 determines that the data is received through the wireless network, the gateway 7 (more specifically, the calculation control means 14) converts a protocol of the received data at “S102” in FIG. 11 and the gateway 7 (more specifically, the calculation control means 14) transfers the data to the control device 8 (the IP node) through the IP network 100 at “S103” in FIG. 11.
For example, if the gateway 7 (more specifically, the calculation control means in the gateway 7) determines that the date is received, the gateway 7 (more specifically, the calculation control means in the gateway 7) transfers the data to the control device 8 through the IP network 100 as shown in “SD31” of FIG. 12.
As a result, it is possible to interconnect a wireless network and another network different from the wireless network by providing the gateway between the wireless network and the IP network, converting the protocol of the received data and transferring the data subjected to the protocol conversion through the gateway.
Moreover, FIG. 13 is a block diagram showing another example of the conventional wireless network system, in which the gateway is particularly doubled. In FIG. 13, 1 to 6 and 8 are the same reference numerals as those in FIG. 6, and a gateway 18 (Primary Gateway) for a normal operation interconnects a wireless network and an IP network, a gateway 19 (Secondary Gateway) for a backup interconnects the wireless network to the IP network, and a IP network 101 is shown.
The wireless node 1 is interconnected to adjacent wireless nodes 3, 4 and 2 using wireless lines “WN41”, “WN42” and “WN43” in FIG. 13. Similarly, wireless nodes 2, 3, 4, 5 and 6 are also interconnected to the adjacent wireless nodes by properly using wireless lines “WN44”, “WN45”, “WN46”, “WN47”, “WN48” and “WN49” in FIG. 13.
Furthermore, the wireless nodes 2, 4 and 6 are interconnected to the gateway 18 using wireless lines “WN50”, “WN52” and “WN54” in FIG. 13 respectively, and the wireless nodes 2, 4 and 6 are interconnected to the gateway 19 using wireless lines “WN51”, “WN53” and “WN55” in FIG. 13 respectively. Thus, a wireless network shown in a broken line of FIG. 13 is established.
In addition, the gateways 18 and 19 are interconnected to the IP network 101, and also the control device 8 is interconnected to the IP network 101.
An operation according to the conventional example shown in FIG. 13 will be described with reference to FIGS. 14, 15, 16, 17, 18 and 19. FIG. 14 is a flowchart for explaining an operation of each wireless node. FIGS. 15, 17 and 19 are diagrams for explaining a data transfer. FIG. 16 is a flowchart for explaining an operation of the gateway 18 for a normal operation. FIG. 18 is a flowchart for explaining an operation of the gateway 19 for a backup.
It is assumed that the gateway 18 for a normal operation and the gateway 19 for a backup are treated as an identical network address. Moreover, it is assumed that specific structures of the wireless nodes 1 to 6 and the gateways 18 and 19 are the same as those in FIGS. 7 and 8.
At “S201” in FIG. 14, the wireless node (more specifically, the calculation control means 10) determines whether to transfer the data to the control device 8 (the IP node) through the IP network 101 or not.
At “S201” in FIG. 14, if the wireless node determines to transfer the data, the wireless node (more specifically, the calculation control means 10) searches a transfer path to the gateway 18 for a normal operation and establishes the transfer path at “S202” in FIG. 14 and the wireless node (more specifically, the calculation control means 10) transfers the data to the gateway 18 for a normal operation using the established transfer path at “S203” in FIG. 14.
For example, if the wireless node 1 (more specifically, the calculation control means in the wireless node 1) determines to transfer the data, the wireless node 1 (more specifically, the calculation control means in the wireless node 1) searches and establishes a transfer path using wireless lines “WN42” and “WN52” in FIG. 15, and transfers the data to the gateway 18 for a normal operation as shown at “SD61” in FIG. 15.
As described above, the gateway 18 for a normal operation and the gateway 19 for a backup are treated as the identical network address. Therefore, at the same time, the data are also transferred from the wireless node 1 to the gateway 19 for a backup through wireless lines “WN42” and “WN53” in FIG. 15 as shown in “SD62” in FIG. 15.
Meanwhile, at “S301” in FIG. 16, the gateway 18 for a normal operation (more specifically, the calculation control means 14) determines whether the data is received through a wireless network or not.
At “S301” in FIG. 16, if the gateway 18 determines that the data is received through the wireless network, the gateway 18 for a normal operation (more specifically, the calculation control means 14) converts the protocol of the received data at “S302” in FIG. 16 and the gateway 18 for a normal operation (more specifically, the calculation control means 14) transfers the data to the control device 8 (the IP node) through the IP network 101 at “S303” in FIG. 16.
For example, if the gateway 18 for a normal operation (more specifically, the calculation control means in the gateway 18) determines that the data are received, the gateway 18 for a normal operation (more specifically, the calculation control means in the gateway 18) transfers the data to the control device 8 through the IP network 101 as shown in “SD71” in FIG. 17.
At “S401” in FIG. 18, moreover, the gateway 19 for a backup (more specifically, the calculation control means 14) determines whether the data are received through the wireless network or not.
At “S401” in FIG. 18, if the gateway 19 determines that the data are received through the wireless network, the gateway 19 for a backup (more specifically, the calculation control means 14) determines whether the gateway 18 for a normal operation is in a normal operation or not at “402” in FIG. 18.
At “S402” in FIG. 18, if the gateway 19 determines that the gateway 18 for a normal operation is not in the normal operation (an abnormal operation), the gateway 19 for a backup (more specifically, the calculation control means 14) converts the protocol of the received data at “S403” in FIG. 18 and the gateway 19 for a backup (more specifically, the calculation control means 14) transfers the data through the IP network 101 to the control device 8 (the IP node) at “S404” in FIG. 18.
For example, if the gateway 19 for a backup (more specifically, the calculation control means in the gateway 19) determines that the data are received, the gateway 19 for a backup (more specifically, the calculation control means in the gateway 19) transfers the data to the control device 8 through the IP network 101 as shown in “SD81” of FIG. 19.
As a result, by providing two gateways, that is, the gateway for a normal operation and the gateway for a backup between the wireless network and the IP network, it is possible to double the gateway and to enhance the reliability.
However, in the conventional example shown in FIG. 6, a communication load of the gateway 7 becomes greater because all communications are carried out through the gateway 7. There has been a problem in that the wireless network cannot be interconnected to the IP network when a fault is generated in the gateway 7.
Since an area in which each wireless node can carry out the communication is limited and only one gateway is provided, moreover, there has been a problem in that setting position of the gateway and that of the wireless node are naturally restricted.
In the conventional example shown in FIG. 13, furthermore, a higher reliability than that in the conventional example shown in FIG. 6 is obtained because the gateway is doubled. In the normal operation state, however, all communications are carried out via the gateway 18 for a normal operation in the same manner as in the conventional example shown in FIG. 6. For this reason, a problem of an increase in the communication load cannot be solved.